AgO versus CuO in the Catalytic Isomerization of Coordinated Diaminocarbenes to Formamidines: A Theoretical Study.

DFT theoretical calculations for the AgO-induced isomerization process of diaminocarbenes to formamidines, coordinated to Mn(I), have been carried out. The reaction mechanism found involves metalation of an N-H residue of the carbene ligand by the catalyst AgO and the formation of a key transition state showing a μ-η:η coordination of the formamidinyl ligand between manganese and silver, which allows a translocation process of Mn(I) and silver(I) ions between the carbene carbon atom and the nitrogen atom, before the formation of the formamidine ligand is completed. Calculations carried out using CuO as a catalyst instead of AgO show a similar reaction mechanism that is thermodynamically possible, but highly unfavorable kinetically and very unlikely to be observed, which fully agrees with experimental results.

The X-ray constrained wavefunction of the [Mn(CO){(CH)P-S-C(Br)-P(CH)}]Br complex: a theoretical and experimental study of dihalogen bonds and other noncovalent interactions.

The synthesis and X-ray structure determination of the [Mn(CO){(CH)P-S-C(Br)-P(CH)}]Br complex (1) are described. The C-Br..

Octahedral manganese(i) and ruthenium(ii) complexes containing 2-(methylamido)pyridine-borane as a tripod κN,H,H-ligand.

The borane adduct of the 2-(methylamido)pyridine anion, [mapyBH], has been incorporated into octahedral metal complexes. In fac-[Mn(κN,H,H-mapyBH)(CO)] (1) and fac-[RuH(κN,H,H-mapyBH)(CO)(PiPr)] (2), which have been prepared by treating K[mapyBH] with fac-[MnBr(MeCN)(CO)] and [RuHCl(CO)(PiPr)], respectively, it behaves as a tripod ligand, attached to the metal atom through the amido N atom and through two H atoms of the BH moiety. X-ray diffraction analyses and theoretical studies (DFT, QTAIM) have shown that the MHB atom grouping of 1 and 2 comprises two 3c-2e M-H-B interactions that are between those of the Shimoi type (κH coordination of the B-H bond) and those of the agostic type (κB,H coordination of the B-H bond).

2-(Methylamido)pyridine-Borane: A Tripod κ(3)-N,H,H Ligand in Trigonal Bipyramidal Rhodium(I) and Iridium(I) Complexes with an Asymmetric Coordination of Its BH3 Group.

The complexes [M(κ(3)-N,H,H-mapyBH3)(cod)] (M = Rh, Ir; HmapyBH3 = 2-(methylamino)pyridine-borane; cod = 1,5-cyclooctadiene), which contain a novel anionic tripod ligand coordinated to the metal atom through the amido N atom and through two H atoms of the BH3 group, were prepared by treating the corresponding [M2(μ-Cl)2(cod)2] (M = Rh, Ir) precursor with K[mapyBH3]. X-ray diffraction studies and a theoretical Quantum Theory of Atoms in Molecules analysis of their electron density confirmed that the metal atoms of both complexes are in a very distorted trigonal bipyramidal coordination environment, in which two equatorial sites are asymmetrically spanned by the H-B-H fragment. While both 3c-2e BH-M interactions are more κ(1)-H (terminal σ coordination of the B-H bond) than κ(2)-H,B (agostic-type coordination of the B-H bond), one BH-M interaction is more agostic than the other, and this difference is more marked in the iridium complex than in the rhodium one.

Generating and trapping metalla-N-heterocyclic carbenes.

By means of a combined experimental and theoretical approach, the electronic features and chemical behavior of metalla-N-heterocyclic carbenes (MNHCs, N-heterocyclic carbenes containing a metal atom within the heterocyclic skeleton) have been established and compared with those of classical NHCs. MNHCs are strongly basic (proton affinity and pK(a) values around 290 kcal mol(-1) and 36, respectively) with a narrow singlet-triplet gap (around 23 kcal mol(-1)). MNHCs can be generated from the corresponding metalla-imidazolium salts and trapped by addition of transition-metal complexes affording the corresponding heterodimetallic dicarbene derivatives, which can serve as carbene transfer agents.

Deprotonation of C-alkyl groups of cationic triruthenium clusters containing cyclometalated C-alkylpyrazinium ligands: experimental and computational studies.

The C-alkyl groups of cationic triruthenium cluster complexes of the type [Ru3(μ-H)(μ-κ(2)N(1),C(2)-L)(CO)10](+) (HL represents a generic C-alkyl-N-methylpyrazium species) have been deprotonated to give kinetic products that contain unprecedented C-alkylidene derivatives and maintain the original edge-bridged decacarbonyl structure. When the starting complexes contain various C-alkyl groups, the selectivity of these deprotonation reactions is related to the atomic charges of the alkyl H atoms, as suggested by DFT/natural-bond orbital (NBO) calculations. Three additional electronic properties of the C-alkyl C-H bonds have also been found to correlate with the experimental regioselectivity because, in all cases, the deprotonated C-H bond has the smallest electron density at the bond critical point, the greatest Laplacian of the electron density at the bond critical point, and the greatest total energy density ratio at the bond critical point (computed by using the quantum theory of atoms in molecules, QTAIM).

QTAIM analysis of the bonding in Mo-Mo bonded dimolybdenum complexes.

A number of local and integral topological parameters of the electron density of relevant bonding interactions in the binuclear molybdenum complexes [Mo(2)Cl(8)](4-), [Mo(2)(μ-CH(3)CO(2))(4)], [Mo(2)(μ-CF(3)CO(2))(4)], [Mo(2)(μ-CH(3)CO(2))(4)Br(2)](2-), [Mo(2)(μ-CF(3)CO(2))(4)Br(2)](2-), [Mo(2)(μ-CH(3)CO(2))(2)Cl(4)](2-), [Mo(2)(μ-CH(3)CO(2))(2)(μ-Cl)(2)Cl(4)](2-), and [Mo(2)(μ-Cl)(3)Cl(6)](3-) have been calculated and interpreted under the perspective of the quantum theory of atoms in molecules (QTAIM). These data have allowed a comparison between related but different atom-atom interactions, such as different Mo-Mo formal bond orders, ligand-unbridged versus Cl-bridged, CH(3)CO(2)-bridged, and CF(3)CO(2)-bridged Mo-Mo interactions, and Mo-Cl(terminal) and Mo-Cl(bridge) versus Mo-Br and Mo-O interactions. Calculations carried out using nonrelativistic and relativistic approaches afforded similar results.

Experimental and theoretical characterization of the Zn-Zn bond in [Zn2(eta5-C5Me5)2].

The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn(2)(eta(5)-C(5)Me(5))(2)], as well as between Zn and ligand C atoms is firmly based on neutron diffraction and low-temperature X-ray synchrotron diffraction experiments. The multipolar analysis of the experimental electron density and its topological analysis by means of the 'Atoms in Molecules' (AIM) approach reveals details of the Zn-Zn bond, such as its open-shell intermediate character (the results are consistent with a typical metal-metal single bond), as well as many other topological properties of the compound. Experimental results are also compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Møller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in the complex.